a curvy user has asked me to give some advice on modelling the head.(with reference to game characters)

For what it is worth here are a few of my thoughts on the subject:-

1. it has all been done before by very skilled people so if you can get permission to use, adapt, modify, re-clothe or paint somebody else' s model that may be the way to go, curvy3d can be very good at doing that sort of thing.

here is a head taken into curvy3d from the makehuman project http://www.makehuman.org you can design a complete figure together with its rigging for free

here is a makehuman figure modified in curvy

2. many people set out to model the human figure accurately and end up very frustrated, it is a time consuming task and the results may be disappointing. If you do wish to model from scratch there are a few things worth considering.

a- have very good reference images with front, back, side views (at least)

b- block out first then refine

c- 3d detail requires extra polygons which later on will create extra work rigging and slow down games

d- look at simon's torso tutorial etc for useful tips

e- every human being is different (obvious but often forgotten)

f- characterizations rather than accurate modelling are much easier to do in curvy3d this is a very quick sculpt and paint but of course if you are willing to spend the timevery good results can be obtained in curvy

g- the figure must be rigged for animation or you will be stuck with one pose

That's good advice to take a model that has already been made and work with it to make your own. There are a lot of models on-line in which to download and use. And Curvy3D is an excellent software for sculpting.